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Mail sent from non users received by users on same domain exchange 2003

Posted on 2011-09-16
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Last Modified: 2012-05-12
I'm receiving alot of spam from non users on my domain addressed to valid users.

I'm running exchange 2003 with the latest service pack along with mail essentials from gfi.

Other spam is being blocked properly.

Any idea's why this is happening?

Thanks
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Question by:john_991
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Expert Comment

by:Mike
ID: 36549861
Just to clarify. Are you receiving mail from your own domain with fake user names?
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Author Comment

by:john_991
ID: 36549909
Yes, sent by fake users with the same domain name addressed to users who are on the domain.

i.e. Sent from abc@ere.com who is not on the domain addressed to xyz@ere.com who is on the domain.
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Expert Comment

by:Govvy
ID: 36550057
This will be spoofing performed by spambots external to your organisation marking the sender field with your smtp address. It is likely that your spam filtering solution has an exception for your domain name which you should remove to address this issue
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Expert Comment

by:Mike
ID: 36550113
Your being spoofed. You should contact you ISP about adding an SPF record to your DNS entries.
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Expert Comment

by:Mike
ID: 36550123
This will be helpfull in the process. Most ISPs will require you to submit the what you what the DNS entry to be.

http://www.openspf.org/
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Expert Comment

by:Mike
ID: 36550240
Just a heads up. If you are being spoofed it is possible other people than the people in your domain may be receiving these spoofed e-mails as well.
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Author Comment

by:john_991
ID: 36551211
I have this already in my dns server (spf record)

ere.com. 60 IN TXT "v=spf1 a ~all"

any other idea's?
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Expert Comment

by:Mike
ID: 36551255
To clarify: In "your" DNS server? Do you mean in your internal DNS (.local, etc) or public (.com, etc).

Also, Check out one of the e-mails headers to see where it actually came from. It is possible that you have a client with a spam-bot doing this.



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Author Comment

by:john_991
ID: 36551294
It's in the external dns server. (my hosting company's dns server)

Will look at the header soon.
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Accepted Solution

by:
Jamie McKillop earned 500 total points
ID: 36551648
Hello,

The SPF records are not going to help unless you have a mail gateway product that implements them. Exchange 2003 doesn't have built-in support. I'm not sure if Mail Essentials uses them. Most mail gateway products have an option to turn on anti-spoofing. This will prevent servers that are not specifically listed as internal from sending mail into your organization using one of your domains. Check the documention or ask GFI support if Mail Essentials has this feature.

JJ
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